The continuous progress of LED material and packaging technology promotes the continuous improvement in luminous efficiency of LED product. The product application covers fields of portable products, billboards, display backlight units, cars, lightings, and so on, so the market scale and development force are quite remarkable. Following the application development of high-efficiency LED product, LED heat dissipation technology has become the issue that every company is keen to solve. Besides, as for the selection of LED heat dissipation substrate, there is difference in design according to conditions including the circuit design, size or light emitting efficiency of LED. However, following the development of high-brightness high-efficiency LED and the application trend of high-density packaging, the heat dissipation problem thereof faces more and more strict tests as the development of CPU. If the problem is not solved in a timely manner, the life and light intensity of LED will be affected. As for the traditional LED, the heat generation is low and the heat dissipation problem is not serious, so the application of copper foil printed circuit board (PCB) for general electronic industry will be enough. However, following the prevalence of high-efficiency LED, copper foil printed circuit board (PCB) is not enough for heat dissipation requirements. In order to ensure the heat dissipation stability of LED and the luminous efficiency of LED grain, it is required to manufacture metal fine circuits on ceramic substrates to solve heat problem. However, the finest circuit width of direct bonded copper (DBC) substrate is about 150 um, and the thermal expansion coefficient thereof is quite high, which is 17 ppm/K, so the difference between it and 4-6 ppm/K of highly insulated Al2O3 or AlN ceramic substrates is quite high. Hence, the stability of heat circulation is always a concern for users.
The manufacturing method of high-efficiency LED heat dissipation substrate with ceramic material comprises four ways, i.e. low temperature co-fired ceramic (LTCC), high temperature co-fired ceramic (HTCC), direct bonded copper (DBC) substrate, and direct plated copper (DPC) substrate. The manufacturing temperature of HTCC is about 1300-1600° C., which makes the selection of electrode material is limited, and the manufacturing cost is quite high. As for LTCC, the co-fired temperature is lowered under about 850° C., but the technology issues including size accuracy and product strength thereof are still required to be broken through. DBC combines Al2O3 and Cu plates by high temperature heating, but the technology issue is that, it's not easy to solve the problem of micro voids between Al2O3 and Cu plates, resulting in bigger challenge to mass production energy and yield rate of the product.
Another technology is direct plated copper (DPC) substrate, and the circuit width thereof is smaller. However, direct plated copper (DPC) substrate has problems of copper removal and electric leakage, and the thermal expansion coefficient thereof is quite high (17 ppm/K), so the difference between it and highly insulated Al2O3 or AlN ceramic substrate (4-6 ppm/K) is quite high. Hence, the stability of heat circulation is a big problem.